Combustion engine

ABSTRACT

A four-stroke internal combustion engine having an even number of cylinders whose combustion chambers communicate in pairs, each pair of associated cylinders having on the one hand a common exhaust valve, a valve for the admission of a first carbureted mixture into the first cylinder, a valve for the admission of air or a leaner carbureted mixture into the second cylinder, a spark plug placed in the path of the first carbureted mixture; the piston of the second cylinder is retarded by a predetermined amount with respect to the piston of the first cylinder and the chamber located above the piston of the second cylinder being shaped to expel the leaner mixture (or air) into the first cylinder shortly after ignition when said piston arrives to its top dead center.

[ 1 Feb. 18, I975 1 COMBUSTION ENGINE [75] Inventor: Francois A. Lagarde, Le Havre,

France [73] Assignee: Compagnie Francois de Raffinage,

Paris. France Filed: Feb. 14, 1973 [21] Appl. No.: 332,375

[30] Foreign Application Priority Data Mallory 123/53 A Mallory .1 123/53 A Primary ExaminerChar1es J. Myhrc Assistant E.\amim'r'lony Argenbright Attorney, Agent, or Firm-Curtis, Morris & Satloril [57] ABSTRACT A four-stroke internal combustion engine having an even number of cylinders whose combustion chambers communicate in pairs, each pair of associated cylinders having on the one hand a common exhaust valve, a valve for the admission of a first carbureted mixture into the first cylinder, a valve for the admission of air or a leaner carbureted mixture into the second cylinder, a spark plug placed in the path of the first carburetcd mixture; the piston of the second cylinder is re tarded by a predetermined amount with respect to the piston of the first cylinder and the chamber located above the piston of the second cylinder being shaped to expel the leaner mixture (or air) into the first cylin der shortly after ignition when said piston arrives to its top dead center.

11 Claims, 6 Drawing Figures PATENTEDFEB18I9F5 3.866.582

SHEET 10F 3 I WM FATENTEU 3,866,582

SHEET 2 BF 3 v 4 FIG. 4

PATENTEU FEB 1 81975 SHEET 3 BF 3 COMBUSTION ENGINE The present invention concerns a new internal combustion and controlled ignition engine, the operationof which causes only a minor pollution of the atmosphere. This engine could be called an internal dilution engine.

It is known that atmospheric pollution caused by automotive exhaust gases is essentially due to the presence in these gases, on the one hand, of incompletely burned hydrocarbons and carbon monoxide and, on the other hand, of nitrogen oxides. Unburned hydrocarbons and carbon monoxide are discharged when one uses too rich a carburetion mixture, whereas the production of nitrogen oxides is principally due to operating the engine at too elevated a temperature.

The richness R of the carburetion mixture is usually defined by the following ratio:

(Pc/Pa) f being the ratio of the weight of the fuel to the weight of the air under functional (i.e., operating) conditions and (Pa/Pa) 5 being the same ratio under stoichiometric conditions. In other words, when there is an excess of fuel, the richness is above 1.0 and in the contrary case, the richness is below 1.0. In practice, in order to obtain good operation of the engine, one choose an overall richness at full charge on the order of 1.15. However, the choice of such a value leads to a discharge into the atmosphere of exhaust gases relatively rich in carbon monoxide and in unburned hydrocarbons. It is not possible, in order to remedy it, to significantly dimish diminish overall richness of the airfuel mixture; because this mixture is heterogeneous and it would then be able to exist in the cylinders with zones where the richness would be equal to or even less than 0.55 (which is the lower limit of flamability of the fuel). These zones, when they are in the vicinity of the spark plug, prevent the propagation of combustion across the whole volume of the combustion chamber. In practice, in conventional engines the richness is not able to be below 0.85.

in order to limit the atmopsheric pollution, several solutions have been proposed: according to one first possibility, one uses a very rich mixture which gives the advantage of eliminating the oxides of nitrogen and catalytic or thermal pots are set up which effect the post-combustion of the carbon monoxide and the unburned hydrocarbons. This solution is, however, costly since it complicates the gas exhaust circuit. Moreover, the consumption of gasoline is increased, and it is a priori paradoxical to try to combat pollution by using too rich a mixture.

In accordance with a second possibility, a lean mixture is used in order to decrease the level of pollution of unburned hydrocarbons. In this case, as previously explained, there is an undesirable heterogeneity in the cylinder. in order to overcome this drawback, certain research work has developed an engine in which an ordered heterogeneity of the mixture is established. For this purpose, the mixture is stratified into zones of richness which decrease as one moves away from the spark plug. The stratification is such that the richness is strong in the region of the spark plug and nowhere less than 0.55 in the regions remote from the spark plug. Engines based on this principle are known in which the mixing of the air and gasoline is effected in situ within the cylinder. The gasoline is injected directly in the direction of the spark plug so that at this place the mixture is rich. The stratification is obtained due to the combination of the overall geometry of the cylinder and the turbulent movement of the mixture in the cylinder. Such engines are, however, difficult to perfect, since it has proven a delicate matter to maintain perfect synchronism between the injection of the gasoline, the distribution of the sprayed layer, and the turbulent movement of the gases. Furthermore, the direct injection of gasoline is an expensive technique;

An object of the present invention is to overcome this drawback. Accordingly, a preferred embodiment of the present invention involves a four-stroke engine with an overall lean mixture, which engine is comprised of an even number of cylinders whose combustion chambers communicate in pairs. Each pair of associated cylinders has a common exhaust valve, an inlet valve for a first carbureted mixture, and a second inlet valve for either a second leaner carbureted mixture or for air. These inlet'valves are arranged in such a manner that the first mixture and the air (or the second carbureted mixture) are admitted into the first and the second cylinders respectively of the pair of associated cylinders. A spark plug is placed in the path of the first carbureted mixture in the first cylinder. The piston of the second cylinder: is retarded by a predetermined amount with respect to, the piston of the first cylinder.

An engine constructed in accordance with the invention may operate, at full load, with an overall richness* of the carbureted mixture equal, for instance, to 0.7. By overall richness is meant the average richness of thef carbureted mixture introduced into the two associated cylinders. The value of the richness of the two carbureted mixtures introduced into the two cylinders respectively depends on the value which is established for the overall richness. For a given value of the overall richness, it is, however, possible to vary the respective richnesses of the carbureted mixtures within relatively wide limits. Thus, for instance, if one establishes a value of 0.7 for the overall richness under full load, the richness X of the first carbureted mixture may be be tween 1.4 and 0.85, while the richness y of the second carbureted mixture will be between 0 and 0.55, with x y/2 0.7.

One particular application of the present invention consists in operating the engine with air being introduced into the second cylinder. This is the application which will be described in detail.

Thus, since the carbureted mixture is introduced into the first cylinder and air is injected into the second cylinder, an organized stratification takes place with the richness of the mixture decreasing from the first cylinder towards the second cylinder. Due to the lag between the two pistons, the piston of the first cylinder arrives first at its upper dead center. The ignition then takes place in a medium which is rich in fuel. During the combustion phase in the first cylinder, the piston of the second cylinder reaches its upper dead center, and due to the provision of a large expulsion surface forces the air into the first cylinder so as to cause an internal dilution of the mixture. The combustion in the first cylinder which has started with a rich mixture terminates with a lean mixture. The excess air present after the initiation of the combustion serves on the one hand to burn the hydrocarbons and the carbon monoxide, and on the other hand to lower the combustion temperature so as to minimize the formation of nitrogen oxides.

In the specification and in the accompanying drawings there is described and shown an illustrative embodiment of the invention and various modifications thereof are suggested, but it is to be understood that these are not intended to be exhaustive, but on the contrary, are given for purposes of illustration in order that others skilled in the art may more fully understand the invention so that they may modify and adapt it in various forms, each as may be best suited to the conditions of a particular use.

One embodiment of the invention will be described by way of example with reference to the accompanying drawings in which:

FIGS. 1 to 6 illustrate the phases of admission, compression, ignition, end-of-combustion, expansion and exhaust respectively of an engine in accordance with the invention.

The engine constructed in accordance with the present invention is a four-stroke engine having an even number of cylinders associated in pairs. For clarity, only two associated cylinders have been shown in the drawing, but the description which follows is in all respects valid also for the other associated cylinders of the engine.

With reference to the drawings, the engine comprises a cylinder casing 1 and a cylinder head 2 assembled in the customary manner. The walls of these casings have chambers 3 in which the cooling liquid 4 circulates.

The cylinder casing 1 has two cylinders 5, 6 separated by the interbore material forming a partition 7. In the cylinders 5, 6 there move the two pistons 8, 9 respectively. The piston 9 is delayed relative to the rotation of the drive shaft by an angle of lag of about 25 as compared with the 258. In other words, the piston 8 arrives at its upper dead center slightly before the piston 9 (see FIG. 3). The cylinder head 2 has on its inner wall a combustion chamber 10, which faces primarily the cylinder 5, and an expulsion surface 11 located above the cylinder 6. The expulsion surface 11 is shaped in such a manner that it is substantially flush with the surface 12 of the piston 9 when the latter is at its upper dead center, while it leaves at the upper part of the inter-bore material 7 a passage 13 for communication between the free spaces 14, 15 of the cylinders 5, 6.

The cylinder head comprises, on the side of the cylinder 5, an admission port 16 connected to the carburetor and controlled by a valve 17 and, on the side of the cylinder 6, an air inlet 18 connected to an air box and controlled by a valve 19. The air and carburetedmixture inlets discharge respectively into the combustion chamber 10 via a bent portion 20, 21 oriented in such a manner that the streams of carbureted mixture and air admitted are injected without appreciably mixing in the cylinder and the cylinder 6 respectively. The cylinders 5 and 6 have in common an exhaust valve 22 and a spark plug 23. The spark plug is fixed in the combustion chamber above the cylinder 5 and in the path of the carbureted mixture between the cylinders 5 and 6.

The operation of the engine in accordance with the invention is as follows:

l. Admission:

This phase is illustrated in FIG. 1. The pistons 8 and 9 move downward and the intake valves 17 and 19 open, thus permitting the carbureted mixture and the air to pass. The carbureted mixture used has, for instance, a richness of the order of 1.3. In view of the geometry of the inlets 20, 21 the two streams of carbureted mixture and air do not mix practically at all and are directed towards the cylinder 5 and the cylinder 6, respectively, in the direction indicated by the arrows F and F2 2. Compression:

This phase is illustrated by' FIG. 2. The valves 17 and 19 close. The pistons 8 and 9 rise. The piston 8 at all times leads the piston 9, so that a small proportion of carbureted mixture passes into the cylinder 6 in the direction indicated by the arrow F During the compression, the richnesses in the cylinders 5 and 6 are therefore l.30 and s respectively.

3. Combustion Expansion:

As shown in FIG. 3, the combustion is commenced at the moment that the piston 8 approaches its upper dead center. The spark given off by the spark plug propagates theflame through the free space 14 and the combustion chamber 10.

During the combustion, while the piston 8 starts its descending movement, the piston 9 arrives at its upper dead center practically in contact with the expulsion surface 11, and therefore pushes the wedge of air of richness 6 into the combustion chamber 10, as indicated by the arrow F (see FIG. 4). The result is that the relatively high value of the richness of the mixture in the cylinder 5 is gradually reduced at the end of the combustion to a small value, of the order, for instance, of 0.7. When the combustion is complete, everything happens as though the ignition had been effected in a rich mixture and the combustion in a lean mixture.

The expansion (FIG. 5) takes place simultaneously in both cylinders S and 6.

4. Exhaust (FIG. 6)

The valve 22 opens, allowing the mixture driven by the pistons 8 and 9 to escape.

The engine in accordance-with the invention discharges into the at'mosphere'gases which are very poor in incompletely burned hydrocarbons, carbon monoxide and nitrogen oxides. As part of the battle against the pollution of the atmosphere, one can therefore advantageously equip automobiles with such an engine.

From a practical viewpoint, this engine will furthermore have the following advantages:

The :costbf-construction of the engine is less than that of a conventional engine, since for the same number of cylinders, the number of valves and of spark plugs of the engine of the invention is smaller.

The consumption of gasoline will also be reduced as compared with that of the conventional engines. Operation with a lean mixture leads to a consumption which is between that of an ordinary gasoline engine and that of a diesel engine.

The carburetion is simplified since the excess of air is such at the end of combustion that the hydrocarbons and carbon monoxide given off will depend little on possible small variations in richness.

The octane requirement of the engine is decreased.

I claim:

1. A fou r-stroke internal combustion engine comprising an even number of cylinders in constant communication therebetween in pairs at the combustion chamber level; for each pair of associated cylinders a com-- mon exhaust valve, a first inlet valve for a first carbureted mixture, and a second inlet valve for air or a second carbureted mixture which is leaner than the first carbureted mixture; the said inlet valves being arranged in such a manner that the first carbureted mixture and the air or the second carbureted mixture are admitted into the first and second cylinders, respectively, of each pair of associated cylinders, a spark plug for each pair located in the path of the first carbureted mixture adjacent the said first cylinder; that volume of the chamber above the piston operative in each second cylinder being smaller than, and shaped to expel the second carbureted mixture or air therein into, that volume of the combustion chamber above the piston operative in each respective first cylinder; the major portion of each said combustion chamber overlying each respective first cylinder and only a small portion thereof overlying each respective second cylinder, an expulsion surface overlying each respective second cylinder adjacent each respective combustion chamber and positioned so as to be closely approached by the piston operative in each said second cylinder when at its upper dead center; and the piston of each said second cylinder is delayed a pedetermined amount with respect to each respective first cylinder, sufficient to delay any substantial expulsion of the air or leaner carbureted mixture into the first cylinder until after ignition.

2. An engine according to claim 1, further comprising a carburetion system constructed to give a first carbureted mixture of richness equal to x and a second carbureted mixture of richness equal to y, the values of x and y being such that x y z 0 and x y/2 is approximately equal to the overall richness selected.

3. An engine according to claim 1, characterized by the fact that the lag of the second piston with respect to the first piston is about 25.

4. An engine according to claim 1, comprising a cylinder casing containing at least one of said pairs of cylinders separated by an interbore mass forming a partition, a head tightly covering the said cylinder casing, the chambers above the pistons of each pair of two cylinders communicating with each other above said partition in order to form a common combustion chamber, an inlet for the first carbureted mixture controlled by said respective inlet valve and discharging through the controlled by said respective inlet valve and discharging through the head in the direction of the said second cylinder.

5. An engine according to claim 4, comprising an expulsion surface shaped in the head in such a manner that it is substantially flush with the upper surface of the piston of the second cylinder when said piston is at its top dead center, while permitting there to remain, with the upper part of the partition, a passage for communication between the two cylinders.

6. An engine according to claim 5 further comprising a carburation system constructed to give a first carbureted mixture of richness equal to x and a second carbureted mixture of richness equal to y, the values of x and y being such that x y z 0 and x y/2 is approximately equal to the overall richness selected.

7. An engine according to claim 5 wherein said first inlet valves are large and are each positioned over said respective first cylinders, wherein said second inlet valves are large and are each positioned over said respective second cylinders, and said common exhaust valves are large and are each positioned between said respective first and second inlet valves.

8. An engine according to claim 7, wherein said first inlet valve and said common exhaust valve are positioned in said combustion chamber and said second inlet valve is positioned in said expulsion surface.

9. An engine according to claim 8, wherein said combustion chamber extends entirely across all of said first cylinder and a small portion of said second cylinder and said expulsion surface extends across the remainder of said second cylinder.

10. An engine according to claim 9, wherein said spark plug is positioned to one side of said combustion chamber between said first inlet valve and said common exhaust valve.

11. An engine according to claim 8, characterized by the fact thatthe lag ofthe second piston with respect to the first piston is about 25.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT N0. 3,866,582 DATED 1 February 18, 1975 iNVENTORtS) Francois A. Lagarde It is certified that error appears in the aboveeidentified patent and that said Letters Patent are hereby corrected as shown below:

The assignee should be -Compagnie Francaise de Raffinage-- instead of "Compagnie Francois de Raffinage";

Claim 1, line 21 "pedetermined" should be ---predetermined--.

Signed and sealed this 10th day of June 1975.

(SEAL) Attest:

C. MARSHALL DAN-N RUTH C. MASON Commissioner of Patents Arresting Officer and Trademarks 

1. A four-stroke internal combustion engine comprising an even number of cylinders in constant communication therebetween in pairs at the combustion chamber level; for each pair of associated cylinders a common exhaust valve, a first inlet valve for a first carbureted mixture, and a second inlet valve for air or a second carbureted mixture which is leaner than the first carbureted mixture; the said inlet valves being arranged in such a manner that the first carbureted mixture and the air or the second carbureted mixture are admitted into the first and second cylinders, respectively, of each pair of associated cylinders, a spark plug for each pair located in the path of the first carbureted mixture adjacent the said first cylinder; that volume of the chamber above the piston operative in each second cylinder being smaller than, and shaped to expel the second carbureted mixture or air therein into, that volume of the combustion chamber above the piston operative in each respective first cylinder; the major portion of each said combustIon chamber overlying each respective first cylinder and only a small portion thereof overlying each respective second cylinder, an expulsion surface overlying each respective second cylinder adjacent each respective combustion chamber and positioned so as to be closely approached by the piston operative in each said second cylinder when at its upper dead center; and the piston of each said second cylinder is delayed a pedetermined amount with respect to each respective first cylinder, sufficient to delay any substantial expulsion of the air or leaner carbureted mixture into the first cylinder until after ignition.
 2. An engine according to claim 1, further comprising a carburetion system constructed to give a first carbureted mixture of richness equal to x and a second carbureted mixture of richness equal to y, the values of x and y being such that x > y > or = 0 and x + y/2 is approximately equal to the overall richness selected.
 3. An engine according to claim 1, characterized by the fact that the lag of the second piston with respect to the first piston is about 25* .
 4. An engine according to claim 1, comprising a cylinder casing containing at least one of said pairs of cylinders separated by an interbore mass forming a partition, a head tightly covering the said cylinder casing, the chambers above the pistons of each pair of two cylinders communicating with each other above said partition in order to form a common combustion chamber, an inlet for the first carbureted mixture controlled by said respective inlet valve and discharging through the head in the direction of the said first cylinder, and an intake for the air or for the second carburated mixture, controlled by said respective inlet valve and discharging through the head in the direction of the said second cylinder.
 5. An engine according to claim 4, comprising an expulsion surface shaped in the head in such a manner that it is substantially flush with the upper surface of the piston of the second cylinder when said piston is at its top dead center, while permitting there to remain, with the upper part of the partition, a passage for communication between the two cylinders.
 6. An engine according to claim 5 further comprising a carburation system constructed to give a first carbureted mixture of richness equal to x and a second carbureted mixture of richness equal to y, the values of x and y being such that x > y > or = 0 and x + y/2 is approximately equal to the overall richness selected.
 7. An engine according to claim 5 wherein said first inlet valves are large and are each positioned over said respective first cylinders, wherein said second inlet valves are large and are each positioned over said respective second cylinders, and said common exhaust valves are large and are each positioned between said respective first and second inlet valves.
 8. An engine according to claim 7, wherein said first inlet valve and said common exhaust valve are positioned in said combustion chamber and said second inlet valve is positioned in said expulsion surface.
 9. An engine according to claim 8, wherein said combustion chamber extends entirely across all of said first cylinder and a small portion of said second cylinder and said expulsion surface extends across the remainder of said second cylinder.
 10. An engine according to claim 9, wherein said spark plug is positioned to one side of said combustion chamber between said first inlet valve and said common exhaust valve.
 11. An engine according to claim 8, characterized by the fact that the lag of the second piston with respect to the first piston is about 25* . 